1. Field of Invention
The invention relates to a structure of measuring the etching speed and the associated method. In particular, the invention relates to a method of detecting the etching speed of a metal layer in a microelectromechanical system (MEMS) manufacturing process.
1. Related Art
In the manufacturing process of microelectromechanical system (MEMS) devices, some suspending structures (the infrared (IR) sensor, micro heater, gas sensor, and pressure sensor in sensors and the accelerator meter, micro motor, and gyroscope in actuators) are needed. The formation of such suspending structures is done by depositing a sacrifice layer, followed by stacking a structure layer, and finally etching the sacrifice layer to put the whole structure in a suspending state. Whether the suspending structure is perfect depends upon whether the etching is complete. The conventional judging method is to use a microscope or scanning electronic microscope (SEM) to view the etched part by naked eyes. However, the efficiency is not good so that such manufacturing process cannot satisfy the need for mass production. On the other hand, most structures that are checked using the microscope or SEM are limited to the cases where the structure layer stacked on the sacrifice layer is made of a transparent material. Thus, the conventional method does not apply to opaque materials. Moreover, in the MEMS manufacturing process, the etching speed control is also another important factor. The method of using the microscope or SEM has also a worse precision.